CW boss Mark Pedowitz has said it before, but he said it again when speaking with reporters at the 2014 summer TV press tour:
"Supernatural" will run as long as Jared Padalecki and Jensen Ackles want to keep playing the Winchester brothers.

"I would love to see 'Supernatural' go beyond Season 10. I'm a big fan of the show. I've seen every episode ... big fan of Jared and Jensen," Pedowitz tells a small group of reporters after his panel. "Look, if the show continues the way it's doing and the boys want to do it, we're in."

But even if the show does end, you might get another spinoff -- Pedowitz says he's open to another. "I would love to get a 'Supernatural' spinoff done. I think it's a great franchise and it's got a lot of legs to it," he says.

The spinoff The CW tried during the 2013-14 season, "Bloodlines," didn't work, because "it did not creatively go where we wanted it to go," he says. "We are very open to doing another spinoff. We're waiting for them to come in with a clever new idea. I would love to get another 'Supernatural' spinoff done. I think it's a great franchise."